Centrifugal separators



Dec. 6, 196,6 G. zlPPE x-:TAL

CENTRIFUGAL sEPARAToRs 2 Sheets-Sheet 1 Filed Nov. 14, 1958 INVENTORSDec. 6, 1966 G. ZIPPE. ETAL CENTRIFUGAL SEPARATORS 2 Sheets-Sheet 2Filed Nov. 14, 1958 vii will.

United States Patent O 3,289,925 CENTRIFUGAL SEPARATORS Gernot Zippe,Charlottesville, Va., and Rudolf Scheffel, Frankfurt am Main,Romerstadt, and Max Steenbeek, Jena, Germany; said Zippe and saidScheffel assignors to Deutsche Goldund Silber-Scheideanstalt vormalsRoessler, Frankfurt am Main, Germanyv Filed Nov. 14, 1958, Ser. No.845,584

Claims priority, application Germany, Nov. 14, 1957 D 26,831; Dec. 28,1957, D 27,109; Austria,

Nov. 28, 1957, A 7,728/57 (Filed under Rule 47 (a) and 35 U.S.C. 116) 6Claims. (Cl. 233-1) The invention relates to an apparatus for theseparation of mixtures of gases or gaseous isotopes by means of acentrifuge operating in a vacuum. More particularly, in contrast withthe prior art, the purpose is to provide a centrifuge which has aself-stabilizing rotating system.

The primary object of the invention is to provide a centrifugal systemwhich requires less power than those normally used and likewise is ofsubstantially lighter constructon, while at the same time this lightenedconstruction does not require special precautions against the explosionof the rotor.

According to the invention the rotor can be rigid or can be madeflexible, and at the same time a favorable ratio between the length anddiameter in relation to the separating efficiency can be obtained.

In order to pass through the critical speed of rotation up to theoperating speed while maintaining a high ratio of length to diameter ofthe rotor, means are provided in connection with the rotor for dampingthe rapid oscillations of the system. It has also been found that a longrotor can be caused to run especially quietly by providing adjustablesupports arranged perpendicularly to the axis of rotation, so that thepassage through the critical speed can be carried out in the shortestpossible time. The supports can for instance be arranged in contact withthe outside of the rotor.

The arrangement of the rotor to turn about a perpendicular axis also`makes it possible to dampen certain vibrations, for example the slowerones, at the upper end and the rapid vibrations in the lower end.

Further objects and advantages of the invention will appear more fullyfrom the following description, especially when taken in conjunctionwith the accompanying drawings, which form a part thereof.

In the drawing FIG. 1 shows in vertical cross-section an apparatusembodying the invention.

FIG. 2 shows in vertical cross-section a modied form of the invention.

In the arrangement according to FIG. 1, the centrifuge housing 1contains a rotor 2 mounted to rotate about a vertical axis. In thebottom of the housing is a suction device 3 connected by passage 3a tothe interior of the housing, in order to maintain a reduced pressuretherein. The rotor contains a steel ring 7, which lies in the range of arotating electric eld which is produced in the winding 8. Thearrangement is such that the rotor runs out of synchronism with theelectric eld until it reaches the desired operating speed when it isautomatically synchronized with the eld. On the outside of the housingare pipe systems 4 through which warm and cold uids such as water can owin opposite directions, in order to produce temperature changes whichare transmitted by radiation to the rotor.

The mixture to be separated is introduced by pipe 5 into the interior ofthe rotation rotor where the temperature differences set the mixtureinto a path of travel in the direction of the arrows 6 and also rotationabout the axis. This circulation is induced by the temperaturedifferential produced by pipes 4 which induce thermal currents in thetluid. Circulation is also improved by the provision in the rotor of areceiving tube 19 which has openings at the ends of its arm facingtowards the direction of rotation of the rotor and which decreases therotational velocity of the gas within the rotor in the vicinity of theopenings and thereby decreases the pressure at the periphery of therotor in this area.

Because the rotor has to pass through its critical speed, it isdesirable to provide damping arrangements, which must be so constructedthat the whole rotating system is self-stabilizing. This can beaccomplished according to the invention by combination bearing anddamping arrangements at the ends of the rotor.

The self-stabilizing can be accomplished by a flexible construction ofthe rotor, in that as shown the rigid parts 2 of the rotor are connectedthrough resilient parts 9. These parts may be in the shape of rings ofan elastic material, such as rubber, elastic synthetic material,metallic springs or the like. braced by the engagement of bracesadjustable perpendicular to its axis of rotation, especially when therotor is passing through its critical speed. Such braces may be wheels10 located close to the outside of the rotor and mounted to turn aboutadjustable perpendicular axes, which brace the rotor while it is passingthrough the critical speed.

For the stabilization of a system rotating about a vertical axis, it isdesirable to have a damping arrangement 11 which operates against slowvibrations in the top of the rotor and an arrangement 12 which operatesagainst rapid vibrations and longitudinal vibrations and combinations ofthese at the lower end of the rotor.

The damping arrangement 11 consists of a metal ring 11a, which isconnected through a stationary cup-shaped body 11b with the housing. Thebody 11b is formed of material with inherent resilience and dampingpower, such as rubber. The damping device 11 is not connected directlywith the rotor 2, but the circular body 11a is formed of a magnetizedmagnetic material, Within the field of which is arranged the upwardextension 11C of the rotor body which is formed of magnetic material.

The damping arrangement 12 consists of a carrier 12a for the lower cupbearing 12b, in which an elastic axis 12a is embedded, which isconnected with the rotor. The carrier 12a is movable and rests in a cup12d lled with oil, so that vibrations of the carrier 12a will be dampedby the oil.

The tube 5 passes through opening 14 in the projection 11C. Thearrangement 19 is built like a Pitot tube, which utilizes the pressureof the material inside lthe rotor and in Vthis manner takes off theheavy fraction to the outside of the rotor. The light tract-ions canpass through opening 14 into the space between the housing 1 and therotor 2 and then to suction device 3 through passage 3a.

A further modification of the invention is shown in FIG. 2. Theconstruction includes a vacuum-tight housing 101 for the thin-walledrotor 102, which is closed at the top and the bottom by lids or covers104 and 103 respectively. The lid 103 carries on its outer side a steelcore plate 105 which is arranged opposite Ia stator winding 106 on theinside of the housing. On the lower side of the lid 103 i-s an elasticflexible axle 107, which rests on a hard metal plate 108 and is guidedin the bushing 109. The bushing is connected with the conical dampingmember 131, which is located in an oil bath 111 in the bearing PatentedDec. 6, 1966 Furthermore, the rotor can be bracket 110. The spring 112provides through its elastic resistance for m-aintaining the desiredposition of the rotor in the housing. The guiding bushing 109 transmitsthe vibrations of the rotor, which are dependent on the rigidity of theaxle and moment of inertia of the rotor, to the damping arrangement 131,which for these vibrations gives a maximum absorption of energy.

The upper lid 104 is provided with a cylindrical projection 113, inwhich a hollow iron cylinder 114 is em-bedded. Above this cylinder is amagnet 115 which is connected to the housing by a damping arrangement116. The stationary pipe systems 117, 118, 119 pass through theprojection 113 and ring 114 with an air space therebetween. The tube 118serves for the introduction of gas and ends somewhere about the middleof the rotor at 120. Tube 119 ends below the upper c-over in transversepipes 121 with openings 122 in their ends. The inner tube 11'7, whichlike the tube 119 serves for the removal of gas, extends to the bottomof the rotor and has laterally extending pipesl 123 provided with inletopenings 124 at their ends in the neighborhood of the outer rot-or wall.

In the bottom of the rotor -above pipes 123 is arranged a rigidseparating lwall 125 with central and peripheral openings 126, 127respectively. The inside of the housing 101 is provided with spiralgrooves 128.

The operation of this centrifuge is las follows:

The driving of the rotor is produced through the operation in the vacuumspace of the three phase winding stator, the plate 105 secured to thebottom cover forming the armature of this winding. The stator is fedwith current of a frequency which causes the desired speed of rotationof the rotor and produces the corresponding Irotating field. Afterbeginning operation asynchronously, the armature is automaticallybrought into synchronism and the speed of rotation of the rotorcorresponds with the frequency of the current. Nothing more is requiredbut this direct and synchronous driving yof the rotor, and noIconnecting elements are necessary which might interfere with theoperation of the centrifuge.

In order to obtain a quiet running of the rotor in a gasultra-centrifuge, it is necessary to operate the rotor in a highlyevacuated housing. Such a vacuum is ordinarily maintained throughcontinuous pumping which requires the use of substantial pumpingdevices, so that such an apparatus is fairly expensive. According to theinvention, however, the rotor alone in connection with the correspondingformation of the housing and with the gasv withdrawal system serves forsealing the rotor, that is, active sealing is produced 'by which thenecessary vacuum is automatically maintained.

The spiral grooves 128 on the inner wall of the housing operate, atsufficiently high peripheral speeds of the rotor, to ydrive back gastending to enter into the evacuated flow space from above. The gasconveyed -up between the outer rotor wall and the housing wall passesthrough the air space between the cylinder 114 and the outer pipe 119into the rotor, and is then driven by centrifugal force to the innerw-all of the r-otor and passes out through the outlet system 121 Iand123. If the rot-or is driven at a peripheral speed of more than 400meters per second, the projections or grooves on the housing walls canbe omitted without losing the desired suction effect on the gas.

The path of the gas in the rotor is from the pipe 118 to the pipes 117,119. This pipe system is held in position at its lower end by an ironcore 129 and a corresponding permanent magnet 130 (sce FIG. 2). Forproducing the circulation of gas inside the rotor a temperaturevariation is not necessary as it is in known constructions, and insteadthe necessary circulation is produced mechanically. Since the gas iindsno resistance in a tangential direction on the separating wall 125 whichturns with the rotor, it can, without interference by the centrifugalforce, move from the middle of the rotor to the separating wall andmaintain the high pressure on this wall. In the other end are. locatedthe transverse pipes 121 with the take-olf openings 122 directly in thegas stream and produce for the rotating gas a substantial resistance. Inthis manner the gas, retarded through the transverse arm, loses thespeed of circulation, so that a part of the centrifugal force isovercome and the gas pressure at the periphery of the rotor will besmaller at this point. From this pressure difference at the end of therotor the necessary circulation for the gas flow through the rotorresults, :so that the device has the further advantage that theenergyrequired for producing the circulation, through mechanical means only,is small.

The lighter gases, those not enriched with heavy components, whichundergoes :a smaller centrifugal effect, pass through the centralopening 126 of the separating wall 125 and are drawn off separately inthe bottom part lof the rotor through the openings 123 of the transversearms 124. The backed-up pressure of the rotating gases produced by theescaping movement in the opening of the transverse tubes produces themovement of the separated fraction through the outlet arrangement. Theresistance to flow in the transverse tube must be so selected that itallow-s to pass the same mixture with the optimum ratio. Outside thisoptimum the prevailing resistance will cause more or less material toflow so that with respect to the passage of gas a predeterminedself-stabilizing results. By connecting in series a number ofcentrifuge/s in cascade, the transmission of any error in one unit tothe next unit of the cascade will be limited, so that such anarrangement gives increased certainty of operation.

Such a centrifuge, having the characteristics described above, can beconstructed very `simply and of light materials and occupy little space.It has -been found that with a peripheral speed of the rotor of morethan 330 meters a second the requirement for the driving power is aboutl0() watts per meter of length, which is much lower than couldheretofore be attained.

While we have described herein some embodiments yo our invention, wewish it to be understood that we do not intend to limit ourselvesthereby except within the scope of the claims hereto or hereinafterappended.

We claim:

1. In a centrifugal separator for gaseous mixtures comprising a vacuumchamber, and an elongated thin-walled hollow rotor, means for mountingthe rotor in the chamber to turn about a substantially vertical axis,said mounting means lin normal operation being located .at the lower endonly of the rotor and including means positively positioning the lowerend of the rotor at all times during rotation thereof while permittingtilting of the upper part of the rotor about its vertical axis, saidrotor and said chamber including at the upper end of the rotor adjacentbut non-contiguous bodies one of which is magnetized while the -other ismagnetic, said bodies being symmetrical about the vertical axis lof therotor and maintaining the rotor axis substantially vertical, said bodiesbeing annular rings, and means forming three separate passages for theintroduction of the gaseous mixture and the removal of the separatedcomponents respectively extending from the outside Of the rotor throughsaid rings into the rotor.

'2. A device as claimed Iin claim 1 in which said mounting meanscomprises an elastic axle.

3. A device as claimed in claim 2, comprising a bushing rotatablyholding said axle, and an oil-damped carrier holding said bushing.

y4. In a ldevice as claimed in claim 1, said mounting means including acarrier, means mounting the carrier for trnovement, and means todamp-such movement of the carrier.

5. In a device as claimed in claim 1, damping means mounting one of saidbodies on the chamber.

6. In a device as claimed in claim 1, means to drive the rotorcomprising means to produce a rotating elec- ;ric field and a steel bodycarried by the rotor within said eld.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS McBain.

Beams et al. 233-24 Cohen et a1.

Beams 233-24 Skarstrom.

6 FOREIGN PATENTS 833,487 3/1952 Germany.

REUBEN FRIEDMAN, Primary Examiner.

5 H. L. MARTIN, E. BLANCHARD, W. S. COLE,

Assistant Examiners.

1. IN A CENTRIFUGAL SEPARATOR FOR GASEOUS MIXTURES COMPRISING A VACUUMCHAMBER, AND AN ELONGATED THIN-WALLED HOLLOW ROTOR, MEANS FOR MOUNTINGTHE ROTOR IN THE CHAMBER TO TURN ABOUT A SUBSTANTIALLY VERTICAL AXIS,SAID MOUNTING MEANS IN NORMAL OPERATION BEING LOCATED AT THE LOWER ENDONLY OF THE ROTOR AND INCLUDING MEANS POSITIVELY POSITIONING THE LOWEREND OF THE ROTOR AT ALL TIMES DURING ROTATION THEREOF WHILE PERMITTINGTILTING OF THE UPPER PART OF THE ROTOR ABOUT ITS VERTICAL AXIS, SAIDROTOR AND SAID CHAMBER INCLUDING AT THE UPPER END OF THE ROTOR ADJACENTBUT NON-CONTIGUOUS BODIES ONE OF WHICH IS MAGNETIZED WHILE THE OTHER ISMAGNETIC, SAID BODIES BEING SYMMETRICAL ABOUT THE VERTICAL AXIS OF THEROTOR AND MAINTAINING THE ROTOR AXIS SUBSTANTIALLY VERTICAL, SAID BODIESBEING ANNULAR RINGS, AND MEANS FORMING THREE SEPARATE PASSAGES FOR THEINTRODUCTION OF THE GASEOUS MIXTURE AND THE REMOVAL OF THE SEPARATEDCOMPONENTS RESPECTIVELY EXTENDING FROM THE OUTSIDE OF THE ROTOR THROUGHSAID RINGS INTO THE ROTOR.